Paz Martínez¹ and Antoni Morros²

¹ Instituto de Biología Fundamental. Unidad de Inmunología, Universitat Autònoma de Barcelona, 08193 Bellaterra (Barcelona) Spain.

² Unitat de Biofísica. Departament de Bioquímica i de Biologia Molecular,Universitat Autònoma de Barcelona, 08193 Bellaterra (Barcelona) Spain

Received 05/06/96; Accepted 06/18/96; On-line 07/01/96

We are greatful to M. Campillo from the Laboratorio de Medicina Computacional, Facultad de Medicina (Universitat Autònoma de Barcelona), for drawing the diagram presented in figure 2. We acknowledge Pilar Fuentes for her contribution in drawing figures 4 and 5 and Antoni Iborra for his help in the final typing of the manuscript; both from the Unidad de Inmunologia (Universitat Autònoma de Barcelona).